Access Type

Open Access Dissertation

Date of Award

January 2021

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biomedical Engineering

First Advisor

Mohammad Mehrmohammadi

Abstract

The uterine cervix plays a central role in the maintenance of pregnancy and the process of parturition. Untimely cervical ripening in early gestation predisposes to preterm labor and delivery, the leading cause of infant mortality worldwide. The current approach to evaluate the status of the cervix relies on digital and sonographic examination, which indicates the morphological changes of the cervix (cervical length). Therefore, assessing cervix tissue composition changes may provide more sensitive evaluations about cervix status beyond cervical length. Photoacoustic (PA) imaging is a relatively new, non-invasive ultrasound (US) based technology that captures acoustic signals emitted by tissue components in response to laser pulses. This thesis study developed a novel imaging system by adding PA imaging in conjunction with a clinical transvaginal ultrasound (TVUS) transducer. The system integrated multiparametric acoustic features, including the B-mode US, US-based shear-wave viscoelastography, and PA imaging, capable of detecting the changes in cervical tissue structures and their chemical compositions. The feasibility of PA imaging to quantify the tissue chemical compositions, such as collagen to water ratio (CWR), total hemoglobin (THb), and oxygen saturation (SO2), were determined and optimized through modeling and experimental studies using tissue-mimicking phantoms and tissue samples. The results demonstrated the PA imaging is sensitive to detect chemical composition changes during cervical remodeling, especially in the changes of CWR. Finally, a laboratory prototype of the transvaginal multiparametric acoustic imaging system was built, tested, and optimized to meet the clinical requirements. Further modifications and research directions are discussed that eventually lead to the development of a clinically applicable system.

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